1. Field of the Invention
This invention relates to a remote center compliance device for an industrial manipulator and, more particularly, to a single stage remote center compliance device having a high degree of translational and rotational compliance.
2. Description of the Prior Art
In the design and construction of industrial manipulators, it is an objective to mimic limited aspects of various human capabilities in order to improve the positional accuracy of industrial manipulators in such tasks as inserting a peg in a hole, mating between two parts, a tool and a part, a part and a fixture and many other mating parts. When parts are of an exact nature and the tools and jigs holding them are precisely located, there are no errors in assembly. Not all surfaces on a part, however, are held to the same tolerance and often the mating surfaces are not in perfectly known positions. The design and construction of mechanical manipulators ultimately involves a compromise between manipulator speed, pay load capacity and positional accuracy in order to cope with the aforementioned problems.
It has been known to utilize remote center compliance (RCC) devices as an aid in overcoming the problems encountered in the use of industrial manipulators for insertion and mating operations. These known compliance devices address these difficulties by functioning as a multi-access float which accommodates positional and angular misalignments between parts. For example, U.S. Pat. No. 4,098,001 and U.S. Pat. No. 4,155,169 both disclose RCC devices employing two stages of movable or deformable elements to provide the necessary combination of independent translational and rotational compliant action. These devices hold a workpiece so that the workpiece can rotate about the point where it engages a mating part and lateral error and angular error are absorbed independently so that the workpiece is responsive to contact forces during insertion, and realignment with the insertion axis is passively accommodated.
It is also known to employ a RCC device having translational and rotational compliance utilizing only a single stage of compliance elements. For example, U.S. Pat. No. 4,414,750 discloses such a single stage RCC device comprising a pair of spaced monolithic members connected by three axially compressible and laterally deformable elements which provide both rotational and translational compliance about a remote center of compliance external to the RCC device. While these types of devices are simpler in construction than the two stage RCC devices, they often do not provide a sufficiently high degree of translational and rotational compliance while still being able to transmit torque. In addition, it is not possible to adjust the stiffness of the RCC device over a sufficient compliance range.
Accordingly, a need still exists for an RCC device having a single stage which is still capable of a high degree of translational and rotational compliance, is capable of easily transmitting torque and in which a range of compliance is achieved by being able to adjust the stiffness of the RCC device.